en_tn/2pe/02/19.md

They promise freedom to them, but they themselves are slaves of corruption

"Freedom" here is an idiom for the ability to live exactly as one wants. Alternate translation: "They promise to give them the ability to live exactly as they want to live, but they themselves cannot escape their own sinful desires" (See: rc://en/ta/man/jit/figs-metaphor)

promise freedom ... slaves of corruption

Peter speaks of people who live sinfully as if they were slaves to sin and need to be released from their captivity. (See: rc://en/ta/man/jit/figs-metaphor)

For a man is a slave to whatever overcomes him

Peter speaks of a person as a slave when anything has control over that person, and that thing as the master of that person. Alternate translation: "For if something has control over a person, that person becomes like a slave to that thing" (See: rc://en/ta/man/jit/figs-metaphor)